Process of precipitation of material from cyanid solutions.



1 v C. W. MERRILL. PRQGESS 0F PRECIPITATION 0F MATERIAL FROM GYANID SOLUTIONS.

APPLIGATION FILLED DBO. 9, 1911.

LQ. v Patented June 3, 191'3.

be treated coming in contact with the zinc,'

UNITED sTATEs "PATENT oEEIcE.

CHARLES W. MERRILL, OF BERKELEY, CALIFORNIA.

PROCESS OF PRECIPITATION OF MATERIAL FROM CYANID SOLUTIONS.

Specication of Letters Patent.

Patented June 3, 1913'.

Application filed December 9, 1911. Serial No. 664,735.

cipitation of Material from Cyanid Solu-l tions, of which the following is a specification.

In practice zinc threads or shavings if necessary, zinc fume or dust have4 heretofore been used in order to precipitate precious metals from cyanid solutions. 4The objections tothe use of threads or shavings of zinc' are, first, the`cost of preparing them, second, that even when tightly packed a number of boxes must be placed in tandem in order to finsure each particle of solution to which results in an unnecessarily large consumptlon of zinc and cyanid, third, the zinc becomes rapidly polarized and coated' and -must be moved and washed'frequently to insure good precipitation; fourth, this frequenthandling'oti'ers opportunity for theft. Hence the use of Zinc dust hasfovercome manyof these objections,larg'sly superseding the use of threads or shavings, but it too has defects which have developed in its use, and some of which are as follows: First, it contains a widely. 'varying proportion of oXidand other impurities, many ofvwhich are not only useless as precipitating med-ia, but destructive of cyanid, or difficult to eliminate in the subsequent refining of the precipitate. Second, the'increase in the use of the zinc fume in this art has resulted in an advance in the cost of this material until it now exceeds that of spelter. Third, the transportation and storage of the fume is attended with danger and abnormal eX- pense on account of its inliammable and eX- plosive nature. Fourth, unless hermetically sealed, it pXidizes rapidly, particularly in hydrometallurgical plants where the atmosphere is humid, thus. resulting in a serlous deterioration of its 'precipitating'eliiclency Furthermore, owing to its well known property of malleability, Zinc itself is comminuted with difficulty by the friction of one zinc surface upon anotherand attempts to Vso produce a pulverulent precipitate for cyanid solutions have not found successful use in the art. i i

Now, I have discovered that if cyanld solutions containing the precious metals be A ypassed through a grinding apparatus, one at least of the grinding surfaces of which is composed of a nonhomogeneous mixture of one or more metallic substances, with an abrasive, such as silica, emery, or corundum, or steel, .preferably incorporated or molded into the grinding surface of the precipitant v or alloy and the mixture of solution, precipitate and precipltant conducted to a'collector or a filter, an econo-mic, easily regulated and metallurgically efficient process results,

which is free from the defects enumerated in the zinc thread and Zinc fume processes and one in which the precipitant can be' easily comminuted.

The method of conducting the process I willbe best understood by reference to the accompanying sheet of drawings forming a part of this specification, which shows one of the many' arrangements of plant in which the process forming the subject of the present invent-ion can be carried out; but the apparatus itself and the arrangement of the same form no part of the invention, and may be varied both in the arrangement and number ofthe parts and of the'entire system from time to time, as may be found necessary according to the'conditions under which the process is applied in practice.

In the drawing U is areceiver for the unprecipitated solution; B, an inlet pipe, C is a discharge pipe, T is a revolving tube mill containing rollers or balls composed wholly or in part of a precipitant and prei' erably lined with the same material and driven from any convenient source of power. C1 is a suction of a pump P, and D is a discharge pipe of the same; c1 and c2 are inlet and outlet valves of the grinding apparatus. 4

F is a filter press shown in this case with the dischargepipe D from the pump forming the feed inlet at the top and with open delivery into a launder L which discharges .the precipitated solution into the receiver E.

The generally preferable method of operation is as follows: the receiver U having been filled with solution to be treated the appropriate valves of the tube mill are opened, the tube mill revolved, the pump P is started and the solution allowed to enter the mill whereupon it is subjected to the grinding action of the same. From the mill T the solution is drawn through the pipe C1 to the pump P, thence forced through the pipe D to the friction press F, and

thencev through the filter F which not only retains the precipitate and precipitant but which also eiects the precipitation ofmore of the metallic contents of the solution and permits the solution to pass into the launder L and thence to the receiver E2 l v I pre-fer to use an alloy having a gallvanic action favorable to precipitation,

into which has been incorporated an abrasive for a grinding surface, because of the increased precipitating efiicien'cy and' the increased comminution resulting thereby, a tube mill for the grinding apparatus containing rollers, or balls of said alloy; and I also .prefer to conduct the recipitation Without such' retardation as will permit of |the settlement of they pulverulent precipipasses through it.

tant and Without exposure ofthe precipi- -tant .and precipitate to the infiuence of oxidation from the grinding apparatus to the filter, or collector, but I do not limit myself tothese special `features, and I may use merely a metallic grinding surface and insert the attritive, inert material in 'a loose condition, into thefinterior of the tube mill either before or while the solution Ia'lso do not limit myself to the precise form of grinding apparatus described above, no-r to the precise .arrangement of the plant nor the aggregation of component parts shown. B ut I employ any form of grinding apparatus IWhether closed or o-pen, and any arrangethe solution through the grinding apparatus as tp'attain a proper proportion be'- tween the'comminuted precipitant and the amount of solution, and this may, of course, be accomplished by the valves c1 and c2.

In cases Where the attritive action is insuiicient to liberate an adequate amountof precipitant, or Where it is desired to reinforce the precipitation by an` increased amount of precipitant, I may add ana'dditional amount of. precipitant or alloy such as zinc fume or zinc shavings, or an alloy in the form of granules or an abrasive either to the collecting tank, to the grinding apparatus', tothe filter, or to the solution at any'convenient point between its discharge from the container Where the precious metals are dissolved from theY ore and the discharge of the solution from the apparatus in which the precipitate and precipitant are collected.

I claimas my invention: A

1. The hereinbefore described process of precipitation of metals from their solutions, which consists in passing the said solutions through a comminuting apparatus in which they are brought in contact with a metallic precipitant `of said metals, in which an abrasive substance has been incorporated.

2. The hereinbefore described process 0f precipitation of metals from their solutions, which consists in passing said solutions through a comminuting apparatus, in Which they are brought in contact with a metallic precipitant of said metals, and in which thc comminution of said plecipitant is intensified by the incorporation therewith of an abrasive substance.

3. fThe hereinbefore described process of precipitation of metals from theirsolutions, which consists in passing the said solutions through a comminuting apparatus in which they are brought in contactwith a metallic precipitant of said metals, with Which precipitant an inert, non-metallic abrasive substance has been incorporated.

.4. 'I he-.hereinbefore described process of precipitation of metals from their solutions Which consists in passing the said solutions through a comminuting apparatus in which they are brought in contact with a metallic precipitant offsaid metal, and intensifying the comminution ofthe said precipitant by the incorporation therewith of an inert, non-metallic abrasive substance.

In testimony, that I claim the foregoing as my invent-ion, I have signed my name in presence of tWo Witnesses, this sixth day oi December, 1911.

CHARLES W. MERRILL.

Witnesses:

vHENRY H. GRAW, GHARLEs ENGEL. 

